Celebrations to mark the planned release of the Iraqi journalist who threw his shoes at George Bush have been put on hold after his release from a Baghdad jail was delayed today.

Muntazer al-Zaidi became an unlikely hero after the widely broadcast incident last December. His family have been preparing a hero's welcome to mark his release.

But many of his relatives broke down in tears after they were told his release has been delayed at least until tomorrow amid more allegations that he has been mistreated in jail.

About 10 family members and scores of journalists had gathered outside Mathana airfield prison, in a volatile Sunni area of western Baghdad. The family, who had driven hundreds of miles from their home in southern Iraq, dispersed after word of the delay spread.

Muntazer's brother Vergam spoke to him by phone from outside the jail. He said: "The release of my brother has been delayed because they say his papers have not been finished. Muntazer's psychological health has collapsed because he had been looking forward to this day for so long.

"Today the guards have been harassing him all morning. My brother called me directly to tell my family and the media, 'Thank you and you should go home today.'"

Vergam threatened to stage a sit-in protest tomorrow if his brother's release was delayed again. He said any celebrations would be kept small owing to concerns for Muntazer's security.

His family has previously alleged that Zaida has been beaten in prison, suffering a broken arm, broken ribs and internal bleeding.

The shoe-throwing protest at the former US president made Zaidi a hero across the Arab world, but it also caused embarrassment to Iraq's prime minister, Nouri al-Maliki, who was standing next to Bush at the time.

Maliki's government is believed to be keen to avoid Zaidi being lionised after his release. Zaidi had been planning to give a press conference under the eyes of the world's media before being flown out of Iraq.

However the release is handled, Zaidi has won the adulation of millions, who believe his act of defiance did what their leaders had been too cowed to do.

Pictures of the president ducking have been etched on walls across Baghdad, made into T-shirts in Egypt, and incorporated into children's games in Turkey.

Bush was unhurt in the incident but was twice forced to duck. Zaidi shouted at him in Arabic: "This is your farewell kiss, you dog! This is from the widows, the orphans and those who were killed in Iraq."

Zaidi's family says he might use his celebrity status to promote humanitarian causes such as the rights of orphans and women.

His employer, al-Baghdadiya TV, expects he will return to work as a television reporter for the station, though some have questioned how he would be able to work again as a journalist in Iraq.

In March, Zaidi was convicted of assault. His three-year prison sentence was reduced to one year because he had no prior record. He is due to be released three months early for good behaviour.